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IRGen: Make copying value witnesses trap for noncopyable types. #64194

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Merged
merged 1 commit into from
Mar 8, 2023
Merged

IRGen: Make copying value witnesses trap for noncopyable types. #64194

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48 changes: 48 additions & 0 deletions lib/IRGen/GenValueWitness.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -731,6 +731,17 @@ static llvm::Constant *getNoOpVoidFunction(IRGenModule &IGM) {
});
}

/// Return a function that traps because of an attempt to copy a noncopyable
/// type.
static llvm::Constant *getNoncopyableTrapFunction(IRGenModule &IGM) {
return IGM.getOrCreateHelperFunction("__swift_cannot_copy_noncopyable_type",
IGM.VoidTy, {},
[&](IRGenFunction &IGF) {
IGF.Builder.CreateNonMergeableTrap(IGM, "attempt to copy a value of a type that cannot be copied");
IGF.Builder.CreateUnreachable();
});
}

/// Return a function which takes three pointer arguments and does a
/// retaining assignWithCopy on the first two: it loads a pointer from
/// the second, retains it, loads a pointer from the first, stores the
Expand Down Expand Up @@ -918,6 +929,33 @@ bool isRuntimeInstatiatedLayoutString(IRGenModule &IGM,
return false;
}

static bool
valueWitnessRequiresCopyability(ValueWitness index) {
switch (index) {
case ValueWitness::InitializeBufferWithCopyOfBuffer:
case ValueWitness::InitializeWithCopy:
case ValueWitness::AssignWithCopy:
return true;

case ValueWitness::Destroy:
case ValueWitness::InitializeWithTake:
case ValueWitness::AssignWithTake:
case ValueWitness::GetEnumTagSinglePayload:
case ValueWitness::StoreEnumTagSinglePayload:
case ValueWitness::Size:
case ValueWitness::Stride:
case ValueWitness::Flags:
case ValueWitness::ExtraInhabitantCount:
case ValueWitness::GetEnumTag:
case ValueWitness::DestructiveProjectEnumData:
case ValueWitness::DestructiveInjectEnumTag:
return false;
}
llvm_unreachable("not all value witnesses covered");
}



/// Find a witness to the fact that a type is a value type.
/// Always adds an i8*.
static void addValueWitness(IRGenModule &IGM, ConstantStructBuilder &B,
Expand All @@ -931,6 +969,16 @@ static void addValueWitness(IRGenModule &IGM, ConstantStructBuilder &B,
B.addSignedPointer(fn, IGM.getOptions().PointerAuth.ValueWitnesses, index);
};

// Copyable and noncopyable types share a value witness table layout. It
// should normally be statically impossible to generate a call to a copy
// value witness, but if somebody manages to dynamically get hold of metadata
// for a noncopyable type, and tries to use it to copy values of that type,
// we should trap to prevent the attempt.
if (!concreteTI.isCopyable(ResilienceExpansion::Maximal)
&& valueWitnessRequiresCopyability(index)) {
return addFunction(getNoncopyableTrapFunction(IGM));
}

// Try to use a standard function.
switch (index) {
case ValueWitness::Destroy:
Expand Down
12 changes: 11 additions & 1 deletion test/IRGen/moveonly_deinit.sil
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Original file line number Diff line number Diff line change
Expand Up @@ -15,6 +15,7 @@ sil_stage canonical
class C {}

// CHECK-LABEL: @{{.*}}8MOStructVWV" =
// CHECK-SAME: @__swift_cannot_copy_noncopyable_type
// noncopyable, nontrivial deinit, pointer aligned
// CHECK-64-SAME: <i32 0x81_0007>
// CHECK-32-SAME: <i32 0x81_0003>
Expand All @@ -27,6 +28,7 @@ struct MOStruct {
}

// CHECK-LABEL: @{{.*}}6MOEnumOWV" =
// CHECK-SAME: @__swift_cannot_copy_noncopyable_type
// noncopyable, enum, nontrivial deinit, pointer aligned
// CHECK-64-SAME: <i32 0xA1_0007>
// CHECK-32-SAME: <i32 0xA1_0003>
Expand All @@ -39,6 +41,7 @@ enum MOEnum {
}

// CHECK-LABEL: @{{.*}}13MOComboStructVWV" =
// CHECK-SAME: @__swift_cannot_copy_noncopyable_type
// noncopyable, non-inline, nontrivial deinit, pointer aligned
// CHECK-64-SAME: <i32 0x83_0007>
// CHECK-32-SAME: <i32 0x83_0003>
Expand All @@ -50,6 +53,7 @@ struct MOComboStruct {
}

// CHECK-LABEL: @{{.*}}11MOComboEnumOWV" =
// CHECK-SAME: @__swift_cannot_copy_noncopyable_type
// noncopyable, enum, nontrivial deinit, pointer aligned
// CHECK-64-SAME: <i32 0xA1_0007>
// CHECK-32-SAME: <i32 0xA1_0003>
Expand All @@ -64,6 +68,7 @@ enum MOComboEnum {
// common layout types.

// CHECK-LABEL: @{{.*}}13MOEmptyStructVWV" =
// CHECK-SAME: @__swift_cannot_copy_noncopyable_type
// noncopyable, nontrivial deinit, byte aligned
// CHECK-SAME: <i32 0x81_0000>
@_moveOnly
Expand All @@ -72,6 +77,7 @@ struct MOEmptyStruct {
}

// CHECK-LABEL: @{{.*}}15MOIntLikeStructVWV" =
// CHECK-SAME: @__swift_cannot_copy_noncopyable_type
// noncopyable, nontrivial deinit, pointer aligned
// CHECK-64-SAME: <i32 0x81_0007>
// CHECK-32-SAME: <i32 0x81_0003>
Expand All @@ -83,6 +89,7 @@ struct MOIntLikeStruct {
}

// CHECK-LABEL: @{{.*}}26MOSingleRefcountLikeStructVWV" =
// CHECK-SAME: @__swift_cannot_copy_noncopyable_type
// noncopyable, nontrivial deinit, pointer aligned
// CHECK-64-SAME: <i32 0x81_0007>
// CHECK-32-SAME: <i32 0x81_0003>
Expand All @@ -96,13 +103,15 @@ struct MOSingleRefcountLikeStruct {
// Even if they don't have deinits, we shouldn't share a vwt.

// CHECK-LABEL: @{{.*}}21MOEmptyStructNoDeinitVWV" =
// CHECK-SAME: @__swift_cannot_copy_noncopyable_type
// noncopyable, trivial deinit, byte aligned
// CHECK-SAME: <i32 0x80_0000>
@_moveOnly
struct MOEmptyStructNoDeinit {
}

// CHECK-LABEL: @{{.*}}23MOIntLikeStructNoDeinitVWV" =
// CHECK-SAME: @__swift_cannot_copy_noncopyable_type
// noncopyable, trivial deinit, pointer aligned
// CHECK-64-SAME: <i32 0x80_0007>
// CHECK-32-SAME: <i32 0x80_0003>
Expand All @@ -112,6 +121,7 @@ struct MOIntLikeStructNoDeinit {
}

// CHECK-LABEL: @{{.*}}34MOSingleRefcountLikeStructNoDeinitVWV" =
// CHECK-SAME: @__swift_cannot_copy_noncopyable_type
// noncopyable, nontrivial deinit, pointer aligned
// CHECK-64-SAME: <i32 0x81_0007>
// CHECK-32-SAME: <i32 0x81_0003>
Expand Down Expand Up @@ -319,7 +329,7 @@ sil_moveonlydeinit MOGenericDeinit { @destroy_generic }
// CHECK-LABEL: define {{.*}} @"{{.*}}13MOComboStructVwxx"
// CHECK: call {{.*}} @destroy_struct(
// CHECK: call {{.*}} @destroy_enum(
// CHECK: call {{.*}} @swift_retain(
// CHECK: call {{.*}} @swift_release
// CHECK-LABEL: define {{.*}} @"{{.*}}11MOComboEnumOwxx"
// CHECK: call {{.*}} @[[COMBO_ENUM_OUTLINED_DESTROY]]

Expand Down